[Elecraft] More KAT500

Thu Nov 15 16:17:41 EST 2012

It's supported by electric fence insulators.

Sent from my iPad
Chuck, KE9UW 
(Jack for BMW motorcycles)

On Nov 15, 2012, at 2:00 PM, "N5GE" <Lists at n5ge.com> wrote:

> 
> I hope you have the ladder-line supported by fire-proof (ceramic)
> insulators in the attic.
> 
> Letting ladder-line touch anything combustible can start a fire.
> 
> Amateur Radio Operator N5GE
> ARRL Lifetime Member
> QCWA Lifetime Member
> 
> On Thu, 15 Nov 2012 13:22:55 +0000, "hawley, charles j jr"
> <c-hawley at illinois.edu> wrote:
> 
>> I use a 1:1 balun at 450 ohm ladder line to get thru the attic and then 4 inch open wire outside to the dipole.
>> 
>> Chuck, KE9UW
>> Lionel Trains, TCA, LCCA, LRRC
>> aka Jack, BMW Motorcycles BMWMOA #224
>> 
>> ________________________________________
>> From: elecraft-bounces at mailman.qth.net [elecraft-bounces at mailman.qth.net] on behalf of Brian Alsop [alsopb at nc.rr.com]
>> Sent: Thursday, November 15, 2012 7:02 AM
>> To: elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] More KAT500
>> 
>> This seems so in many cases but it is very doublet length dependent.
>> 
>> I ran one case in TLW with 45' of 450 ohm line that came out as 13 ohms.
>> With a 4:1 balun you'd probably be dropping this further.  High
>> current and most likely not a match.
>> 
>> The best suggestion is to model the antenna at height, get it's
>> feedpoint impedances at bands of interest.  Then go into a program like
>> TLW with the 450 ohm line length and see what impedance results at the
>> shack end.
>> 
>> Adjusting 450 ohm length or doublet length may be required for an
>> adequate compromise on the bands of interest.
>> 
>> Without some analysis (or a proven design) it will be a crap shoot.
>> 
>> 73 de Brian/K3KO
>> 
>> On 11/15/2012 12:31, Jim Wiley wrote:
>>> Ed  -
>>> 
>>> According to Elecraft, the KAT500 can match 10:1 SWR at 500 watts, on
>>> any band 80 to 10 meters.  It can also match 3:1 SWR at 1000 watts on
>>> those same bands.   The 160 meter and 6 meter capabilities are a bit
>>> more limited, but it will still match a fairly wide range of loads.  By
>>> inference, 10:1 SWR at 500 watts between 3 and 30 MHz could result in
>>> peak voltages in the range of 2250 volts and peak currents of 42 amperes
>>> RF  (one or the other, not simultaneously). This is pretty impressive
>>> for a box that size.
>>> 
>>> Using those voltages as limits, that indicates that the KAT500 could
>>> handle power levels of about 250 watts at a 14:1 SWR.  Any more could
>>> result in damage.  I would suggest replacing the 300-ohm line on the
>>> antenna with 450-ohm ladder line, and inserting a 4:1 balun between the
>>> antenna and the KAT500.  I suspect that this will reduce the SWR
>>> excursions, and may get you "inside the envelope" for what the KAT500
>>> can handle.
>>> 
>>> A commonly used antenna is a doublet (dipole) fed with open wire, a 4:1
>>> balun, and a coupler.  Most installations use a length of RG-8 coaxial
>>> cable (typically 10 to 20 feet, but no longer than necessary) to "get
>>> through the wall" - or from the coupler to the balun immediately outside
>>> the building, then the open wire line connects to the balun at that
>>> point and continues to the antenna. 450-ohm ladder line is usually a
>>> better choice because it is designed for transmitting use, where 300-ohm
>>> line is usually "TV lead-in" and not particularly suited for use at
>>> higher power.  Some transmitter rated 300 ohm line exists, and if you
>>> have that type, it may work for you.  As with all open-wire type lines,
>>> keep the line at least 8" to 12" from metal objects if possible, more is
>>> better, and avoid abrupt right angle turns.
>>> 
>>> - Jim,  KL7CC
>>> 
>>> 
>>> 
>>> 
>>> 
>>> On 11/15/2012 2:41 AM, Goss, Ed wrote:
>>>> Hi Jim,
>>>>      Thanks for the info.  I am at work now and unable to post back to
>>>> the group, but I appreciate the explanation. For the low bands, I use
>>>> a 135 ft inv vee center fed with 300 ohm line, with a 1:1 balun near
>>>> the shack. When my KAT500 starts to tune itself, I am seeing high
>>>> SWRs, such as 14:1. After the auto tune cycle, it's 1:1.  Perhaps I
>>>> should be concerned that even with 100 watts, there would be
>>>> conditions that overstress KAT500 internal parts with this type of
>>>> antenna, but I want to be very careful about not damaging the tuner.
>>>> I'm not quite sure how a user would know these limits, or if the
>>>> KAT500 protects itself in any way. Perhaps the KAT500 is meant to work
>>>> with antennas that present a somewhat better match to start with, like
>>>> a typical 80 meter dipole which is cut for CW but the user wants to
>>>> use all the way up to 4.0 MHz...
>>>> --Ed---
>>>> 
>>> 
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>> 
>> 
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